Heat-related illness can range from mild conditions such as rash or cramps to very serious conditions such as heat stroke.​

Last updated:
31 July 2013

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In Australia, every year, hot weather and heat waves cause illness, hospitalisations and sometimes death. It is important that everybody is aware of the signs and symptoms of heat-related illness in order to recognise and treat affected people promptly.

The best way to prevent heat-related illness is to drink plenty of water and to stay as cool as possible. Remember the 4 key messages to keep you and others healthy in the heat:

What is heat-related illness?

Heat-related illness includes dehydration, heat cramps, heat exhaustion, heat stroke and worsening of existing medical conditions. If you have a medical condition such as heart disease, diabetes, or kidney disease and if you take certain medications, heat can make your symptoms worse.

How does heat affect the body?

It is very important that a person’s body temperature stays in the range of 36.1 – 37.8°C. If body temperature rises above this, a person may develop heat-related illness. When the weather is very hot, the body has to work very hard and produce a lot of sweat to keep itself cool. It is more difficult for a person to sweat if it is humid, or if the person is already dehydrated.

Exposure to high temperatures can make existing illnesses seriously worse (for example trigger a heart attack), cause serious permanent injuries (damage to the brain or other vital organs) as a result of untreated heat stroke, and in extreme cases result in death.

What are the health effects and how are they treated?

Heat-related illness includes dehydration, heat cramps, heat exhaustion, heat stroke, and worsening of existing medical conditions. The most common health problem during periods of hot weather is worsening of existing medical conditions. The best way to prevent heat-related illness is to drink plenty of water and to stay as cool as possible.

Dehydration

Mild to moderate dehydration makes the heart work faster and leads to reduced fluid available for sweating.

Symptoms

Dizziness and tiredness

Irritability

Thirst

Bright or dark yellow urine

Loss of appetite

Fainting

What to do – first aid

Drink plenty of water or diluted fruit juice (1 part juice in 4 parts water) and avoid tea, coffee or alcohol

Move somewhere cool, ideally air-conditioned

If possible use a spray bottle with water to cool yourself down

If you start to feel unwell, seek medical advice

Heat cramps

Heat cramps usually affect people who sweat a lot during strenuous activity (e.g. sport or gardening). The sweating causes the body to lose salt and water. The low salt levels in the muscles may be the cause of heat cramps and they can be a symptom of heat exhaustion.

Symptoms

Muscle pains

Muscle spasms

What to do – first aid

Stop all activity and lie in a cool space, legs slightly raised

Drink water or diluted fruit juice (1 part juice in 4 parts water)

Have a cool shower or bath

Massage your limbs to ease spasms, apply cool packs

Do not return to strenuous activity for a few hours after the cramps subside (exertion may lead to heat exhaustion/heat stroke)

Seek medical advice if there is no improvement

Heat exhaustion

Heat exhaustion is the body’s response to an excessive loss of water and salt contained in sweat. If heat exhaustion is not treated, it can turn into heat stroke.

Symptoms

Heavy sweating (cool and moist skin)

Pale skin

Fast and weak pulse rate

Shallow and fast breathing

Muscle weakness or cramps

Tiredness and dizziness

Headache

Nausea or vomiting

Fainting

What to do – first aid

Move to a cool place, ideally air-conditioned and lie down

Remove excess clothing

Take small sips of cool fluids

Take a cool shower, bath or sponge bath

Put cool packs under armpits, on the groin, or on the back of the neck to reduce body heat

If symptoms worsen or if there is no improvement, seek urgent medical advice and call an ambulance if necessary

Heat stroke

Heat stroke is a life-threatening emergency and occurs when the body temperature rises above 40.5°C. Immediate first aid is very important, aim to lower body temperature as quickly as possible.

Symptoms

Sudden rise in body temperature

Red, hot and dry skin (sweating has stopped)

Dry swollen tongue

Rapid pulse

Rapid shallow breathing

Intense thirst

Headache

Nausea or vomiting

Dizziness or confusion

Poor coordination or slurred speech

Aggressive or bizarre behaviour

Loss of consciousness, seizures or coma

What to do – first aid

Immediately call 000 and ask for an ambulance

Get the person into the shade, lay them down, and keep them as still as possible

Give small sips of cool fluids if conscious and able to drink

Bring their temperature down using any method available (sponging with cool water, cool shower, spraying with cool water from a garden hose or soaking clothes with cool water)

Put cool packs under armpits, on the groin, or on the back of the neck to reduce body heat

Do not give aspirin or paracetamol; they do not help and may be harmful

If unconscious, lay the person on their side (recovery position) and check they can breathe properly

Perform CPR if needed

Who is at risk?

Everyone needs to take care in hot weather but some people are at greater risk of serious health effects from the heat than others, including: